Our invention relates to elastic waveguides and, in particular, to guides for propagating elastic waves in inhomogeneous solids. Elastic waves in solid media are also commonly called acoustic, or ultrasonic, waves even though they are not audible to the human ear.
U.S. Pat. No. 3,922,622 issued to G. D. Boyd and L. A. Coldren on Nov. 25, 1975, which is hereby incorporated by reference, discloses a form of waveguide for acoustic waves. An illustrative embodiment of that waveguide comprises an elongated central core region and a core-enclosing region therearound, both regions being composed of materials in which elastic waves can be propagated. The two regions are so chosen that they focus and contain energy predominently within the core region. Advantageously, this waveguide has low propagation loss and low velocity dispersion over frequency bands of interest. In addition isolation from external supports is very good.